Rotary electromagnetic indicator

Abstract

A rotary electromagnetic decade indicator having a permanent magnet rotor with ten alternating north and south salient poles, a salient pole stator with primary and secondary salient poles in one-half digit out of phase relationship and a master salient pole with a relatively wide pole face with sections thereof in full digit phase relationship with the primary and secondary poles and a stator winding on the master pole for magnetizing the master pole in either direction and the remaining primary and secondary salient poles in the opposite direction for stepping the rotor one count.

I claim: 
     
       1. In a rotary electromagnetic indicator comprising an indicating rotor with an even plurality of equiangularly spaced digital indicating positions and having a permanent magnet with an annular arrangement of an even plurality of alternating north and south salient poles for said plurality of equiangularly spaced digital indicating positions respectively, and a stator with a stator core with a plurality of angularly spaced salient poles, each adapted to be aligned with each pole of the rotor permanent magnet as the indicating rotor is rotated by the stator in a forward angular direction through 360°; the improvement wherein the salient poles of the stator core comprises a master salient pole with forward and rearward angular pole face sections in approximately one-half digit out of phase relationship and first and second groups of salient poles with respective pole faces in approximately one-half digit out of phase relationship, each pole face of the first salient pole group being angularly spaced from the rearward pole face section of the master salient pole for respective alignment with rotor poles of opposite polarity, the second salient pole group having at least one more salient pole than the first group, and each pole face of the second pole group being angularly spaced from the forward pole face section of the master salient pole for respective alignment with rotor poles of opposite polarity, and a stator coil winding on the master salient pole for selectively magnetizing the master salient pole in each direction and the remaining salient poles of the stator in the opposite direction for indexing the rotor one digit in said forward angular direction. 
     
     
       2. A rotary electromagnetic indicator according to claim 1 wherein the first pole group comprises only one salient pole. 
     
     
       3. A rotary electromagnetic indicator according to claim 1 wherein the second pole group comprises four salient poles. 
     
     
       4. A rotary electromagnetic indicator according to claim 1 wherein the indicating rotor comprises an annular arrangement of ten salient poles for angularly positioning the indicating rotor in each of ten equiangularly spaced digital indicating positions. 
     
     
       5. A rotary electromagnetic indicator according to claim 1 wherein the stator core comprises an annular ring generally coaxial with the indicating rotor and wherein the salient poles of the stator extend radially inwardly from the annular ring within a plane generally normal to the axis of the indicating rotor. 
     
     
       6. A rotary electromagnetic indicator according to claim 1, 2, 3, 4 or 5 wherein the master salient pole has a continuous pole face, forming said forward and rearward angular pole face sections, with an angular width at least approximately equal to the angular spacing between digital indicating positions. 
     
     
       7. A rotary indicator according to claim 1, 2, 3, 4 or 5 wherein the salient poles of the rotor and the first and second groups of salient poles of the stator have respective pole faces with an angular width approximately equal to one-half the angular spacing between digital indicating positions. 
     
     
       8. A rotary electromagnetic indicator according to claim 1 further comprising reset abutment means selectively operable for preventing rotation of the indicating rotor in said one angular direction past a predetermined digital indicating position. 
     
     
       9. In a rotary electromagnetic indicator comprising an indicating rotor with an even plurality of equiangularly spaced digital indicating positions and having a permanent magnet with an annular arrangement of an even plurality of alternating north and south salient poles for said plurality of equiangularly spaced digital indicating positions respectively, and an electromagnetic stator with a stator core having an annular ring and a plurality of angularly spaced salient poles with pole faces within a plane generally normal to the axis of the indicating rotor, each of the salient poles of the stator being adapted to be aligned with each pole of the rotor permanent magnet as the indicating rotor is rotated in a forward angular direction through 360° by electromagnetic operation of the stator; the improvement wherein the plurality of salient poles of the stator comprises a master salient pole with forward and rearward angular pole face sections and first and second groups of slave salient poles with respective pole faces in approximately one-half digit out of phase relationship, the first group having at least one slave salient pole with a pole face angularly spaced from the rearward pole face section of the master salient pole for respective alignment with rotor poles of opposite polarity, the second group having at least one more slave salient pole than the first group and with their pole faces angularly spaced from the forward pole face section of the master salient pole for respective alignment with rotor poles of opposite polarity, and a salient pole winding on said stator core for magnetizing the stator core to provide one magnetic polarity at the master pole face sections and the opposite polarity at the remaining slave pole faces and operable for digitally indexing the indicating rotor in said forward angular direction from each rest digital indicating position thereof to its succeeding digital indicating position by energizing the winding for a controlled time interval and in a controlled direction.